Charles e



(No Model.)

I o. E. SGRIBNER.

TELEPHONE CIRCUIT.

llllllI 5am/w ya@ 1309 @www UNITED ASTATES PATENT OEEICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR TO 'lll-IE IVESTERN ELECTRIC COMPANY, OF SAMEPLACE. i

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 574,005, dated December 29, 1896.

Application filed April 20, 1895. Serial No. 546,483. (No model.)

To a/ZZ whom it may concern: of two parallel branches of the return-circuit Be it known that I, CHARLES E. SCRIBNER, and the other half of the primary helix in the a citizen of the United States, residing at therbranch,the normal resistances of these Chicago, in the county of Cook and State of two branches being made approximately 5 Illinois, have invented a certain new and equal. The primary helix is placed in the useful Improvement in Telephone-Circuits, usual inductive relation to the secondary (Case No. 383,) of which the following is a helix of the induction-coil. I prefer, howfull, clear, concise, and exact description, refever, to divide this secondary helix also into erence being had to the accompanying drawtwo portions, "from a point intermediate of 6o 1o ing, forming a part of this specification. which portions the return-circuitis branched. My invention relates to the apparatus and The receiving-telephone should also be proarrangement of circuits for te ephones in vided with two magnet-coils included in the which the transmitters are supplied with curtwo sides of the line-circuit, respectively. rent over the line-circuit. Its object is to When the apparatus is thus arranged, tele- 15 prevent interference or cross-talk arising phonic or voice currents circulating in the Afrom induced currents in the conductors of metallic line-circuit traverse the secondary the line-circuit. l helix of the induction-coil and the two inag- It has been proposed to supply transmit nets of the receiving-telephone in the proper ters at substations of telephone systems with direction to magnetize the telephone and re- 7o 2o current traversing both conductors of the produce the transmitted sounds therein. The line-circuit in parallel and returning through su pply-current iiowing over the two sides of a ground connection or a separate returnthe line-circuit in parallel does not affect wire, the' telephone-transmitter at the subthese instruments. It divides into equal porstation, together with the primary winding tions, which traverse the two halves of the 25 of the induction-coil, being included in the primary helix in opposite directions, leaving separate return-circuit branching from the the core neutral; but when the resistance of united conductors of the line-circuit. In the transmitter is altered the distribution of such a system the undulations of current procurrent through the divisions of the primary duced by the transmitter in the ground helixis altered and a resultant magnetization 8o 3o branch are propagated through the line-cirof the core is produced, which creates in the cuit, and since these currents are of thesame secondary helix a current which traverses direction in both line conductors the usual the line-circuit in a manner well understood. expedient of arranging thetwo conductors When, however,rthe conductors of the lineof the metallic circuit in proximity, in order circuit are subjected to the inductive action 35 that they may annui the inductive effect of of adjacent circuits, the currents thus created each other upon contiguous line conductors, in the two conductors lind circuit through the is ineffective in preventing the induction of magnets of the receiving-telephone and the similar currents in neighboring lines. My two divisions of the primary helix in reverse invention applies to this type of apparatus directions, so that they annul each others 9a f 4o and is designed to prevent currents thus inmagnetic effect upon the cores of these induced in the same direction in the two ccnstruments. The receiving-telephone thus reductors of a circuit from laffecting' the telemains unaffected by the currents from an exphone in its circuit; in other words, to pretraneous source. vent the injurious edects ofthe induced cur- I have illustrated my invention in the ac- 4 5 rent in the telephone rather than to prevent companying diagram, which represents four the production of such currents in the telesubstations equipped with the apparatus of phone-line. my invention supplied with current from a 1n my invention I divide the primary helix centrally-located battery and having fa comof thetelephone induetion-coilintotwo equal mon ground return-circuit. The different 1c@ 5o portions and include one half of the inducstations are designated A, B, C, and D. At tion-coil, together with the transmitter, in one each station is located a receiving-telephone c, a transmittingtelephone f, and an induction-coil c/conventionally represented as a closed-circuit transformer. Various modes of arranging the apparatus are shown at the different substations. At station A the receiving-telephone e carries two coils c c2, which are included in the line conductors l and 2, respectively, to the substation apparatus. The line conductors are united through the secondary helix g2 of induction-coil g. From the central point of this helix g2 a ground branch 3 is taken. This ground branch is connected with the central point of the primary helix g of the induction-coil, whose free terminals are grounded through the transmitting-telephone f and the resistance-coil h, respectively. That is, the ground branch 3 is divided into two parallel portions 4 and 5, one of which includes one half of the helix g/ and the transmittilig-telephone f and the other the remaining portion of the helix g and the resistance-coil 7L.

At station C the apparatus is substantially the same, excepting that the resistance-coil h in the branch 5 is omitted, the portion of the primary helix g included 'in that circuit being made of sufficiently high resistance to equal that of the entire branch 4.

The substations A and B are united by line conductors l and 2 in a metallic circuit. Stations C and D are also in a metallic circuit 9. Areturn-conductor lO extends to all the substations in common. Between the conductors l 2 is connected a bridge-wire 1l, which includes two impedance-coils i and t. A bridge 12 is likewise connected across the circuit 8 9, including other impedance-coils i2 and 3. A battery 7t,which is designed to serve as a common source of current-supply for the different substations, has one of its terminals connected with the common return-conductor lO, its other terminal being branched to the different conductors 1l and l2 at points intermediate of the impedance-coils in them.

The line conductors l 2 and 9 maybe assumed to be arranged in close proximity to each other, as in a cable, which results in the induction of voice-currents from one circuit into another.

The 'normal operation of the system in telephonic communication between two connected substations may first be traced. Current from battery 7c finds circuit through t-he impedance-*coils i' and z", which should be of comparatively low resistance, over line conductors l 2 in parallel to the substation, as A, Where it fiows through the two magnet-coils c e2 of the receiving-telephone, through the different portions of the secondary win-din g vg2 of the ind uction-coil, thence through conductor 3, dividing into equal portions through the branches 4 5, and finally to the returnconductor lO. The currents through the magnet-coils and those through the two portions of the secondary winding g2 and the primary winding g' of the induction-coil are in such direction as to annul each others magnetic effects, leaving the cores neutral. If nowr the resistance of the transmitting-telephone f be diminished by the impact of a sound-wave upon it, current is diverted from the branch 5 to branch 4, whereby the magnetic effect of one half of helix g is increased and that of thc other half is decreased. The neutral relation of these helices is disturbed and a resultant magnetization is created in the core, which produces an electromotive force in helix g2. Current is thus caused to flow through the line conductors l 2 to station B through the magnets e e2 of the receivingtelephone and through the secondary winding of the induction-coil. It will be observed that this current flows through the coils e c2 in such direction that they coperate in magnetizing or demagnetizing the core. Hence the receiving-telephone at station B responds to the current thus originated at station A. The succeeding increase of resistance of transmitter f at station A now diverts current from branch 4 and through branch 5. The resultant magnetization of the corev of coil g is now 4in the reverse direction, whereby a reverse current is induced in the line-circuit and a reverse eiect is produced on the receiving-telephone at station B. Thus a succession of soundwaves impinging upon the diaphragm of transmitter f creates in the metallic circuit l 2 and through the receiving-telephones at the two stations a telephonie current of alternating character.

The variation of resistance in the transmitter of course resultsin a variation in the supply-current over conductors l 2 and through the return branch 3 and the return-circuit l0. The supply-current is hence of a slightly undulatory character, the undulations corresponding also to the sound-waves which strike the transmitter. These undulations produce no effect upon the receiving-telephone at the distant station, however, since they traverse bot-h line conductors l and 2 in the same direction and find circuit through the magnetcoils of the receiving-telephone to return conductor 10 in the proper direction to ann ul each other and leave the receiver-magnet unaffected.

Considering now the action of circuit-s in inductive relation upon each other, it will be obvious that the alternating telephonic currents-those which are relied upon in transmitting conversation between substationsdo not affect neighboring circuits. These currents circulate in each metallic circuit, being in opposite directions in the two limbs of the metallic circuit, so that the resultant effect upon adjacent conductors is m'Z. The undulations propagated through the two line conductors of the metallic circuit in the same direction, however, induce in the neighboring metallic circuits other currents which flow along the two line conductors of each circuit in the same direction. These induced currents reaching a substation traverse the mag'- net-coils of the receivinghtelephone and the IIO windings of the induction-coil in the proper direction to leave their cores unaffected, as before traced at length. In short, the operation of the telephonic appliances at a substation may be regarded as resulting in three distinct currents in each line-circuit-a con tinuous current for supplying the transmitter, an undulating current produced in Vthe line conductors coupled in parallel, and an alternating telephonie current circulating in the complete metallic circuit-traversing the line conductors in opposite directions. The substation apparatus at the distant station is undisturbed by both the constant supplycurrent and the undulating current, whether this latter arises in the same circuit from variations of its resistance or whether it be due to the inductive action of adjacent circuits, the receiving-telephone responding only to the alternating telephonie currents circulating in the line and reproducing the sounds represented by that current.

Various departures may be made from the form of my invention which I have herein described, and it may be adapted to other uses than in connection with telephone-circuits.

I claim, broadly, as new-- l. The combination in a telephone-circuit, of an induction-coil, a telephone-transmitter in a closed circuit with the primary helix thereof, anda supply-circuit connected with the central point of said primary helix, the secondary helix of the induction-coil being included in circuit with a receivingtelephone, whereby variations of current in the supply-circuit are prevented from producing undulations of current in the secondary helix.

2. The combination in a telephone-circuit, of an induction-coil having` its primary helix in two portions, adapted when traversed serially by a current to magnetize the core of the coil, a current-supply circuit divided into two parallel branches, each branch including one of the portions of said primary helix, a transmitting-telephone in one of the branches, the normal resistances in the two branches being approximately equal, and a receivingtelephone in circuit with the secondary helix of the induction-coil.

3. The combination with a current-supply circuit comprising the two line conductors of a telephone-line grouped in parallel, and a single returncircuit, the return-circuit being divided at one point into two parallel branches, of a receiving-telephone having two magnet-coils in the different line conductors, respectively, arranged to respond to current circulating in the line-circuit, an induction-coil having its secondary helix in the line-circuit and its primary helix divided into two portions included respectively in the two branches of the return-circuit, a transmitting-telephone in one of said branches, the normal resistances of the branches being approximately equal, the two portions of the primary helix being so related as to direction of current through them that equal currents in the same direction through both branches neutralize each others effects, whereby variations in the supply-current are prevented from aecting the receiving-telephone.

4. The combination with a metallic-circuit telephone-line, of a receiving-telephone at each terminal station thereof having a magnet-coil in each line conductor, the magnetcoils being` arranged to neutralize each other when traversed by currents of the same direction in the line conductors, a supply-circuit comprising the two line conductors grouped in parallel and a single return-conductor, an induction -coil at each station havin g its secondary helix in the line-circuit and having its primary helix 4divided into two portions in ditferent parallel branches of the return-circuit, and a transmitting-telephone in one of the branches, the normal resistances of the branches being approximately equal, substantially as described.

5. The combination with a telephone-circuit and a supply-circuit for the transmittingtelephone thereof, of an induction-coilhav-` ing one of its windings included in the telephone-circuit and the other of its windings in the supplycircnit or a portion thereof, a transmitting-telephone in the supply-circuit, and circuit connections about said transmitting-telephone completing a local circuit wherein the transmitting-telephone may create variations of current strength, said local circuit being in inductive connection with said telephone-line, the winding of the induction-coil in the supply-circuit being adapted to oppose the currents in the telephone-circuit created by current in said local circuit, substantiallyas described.

In witness whereof I hereunto subscribe my name this 17th day of April, A. D. 1895.

CHARLES E. SCRIBNER. Witnesses:

ELLA EDLER, DUNCAN E. WILLETT. 

